Solid state electricity meters are widely used by electric companies to monitor the amount of electricity consumed by customers. When manufacturing utility meters, it is important to keep costs down while retaining full meter functionality. Lower costs allow the meter manufacturer to either increase profits per meter, or pass on the lower costs to its customers, thereby providing the meter manufacturer with a competitive advantage. To this end, even the slightest savings in meter manufacturing costs (e.g., pennies per meter) can be important, especially for meters sold on a large scale, such a residential electricity meters.
One area in which meter savings can be realized is in the bi-directional communications interface included on the meter. Modern solid state electricity meters include a receiver and a transmitter used for bi-directional communication between the meter and the electric company or meter manufacturer. Some modern high functionality meters include sophisticated transmitters and receivers for communicating in a wide variety of environmental conditions. However, most residential electricity meters only require basic receivers and transmitters, as communications required by residential electricity meters are typically limited to the controlled environments of the manufacturing floor and the meter shop of the electricity company. One example of a situation where communication activities are required for residential electricity meters is during calibration of the meter. Another example situation where communication activities are required for residential electricity meters is during meter set-up before the electric company installs the meter at the customer's residence. Because of the limited situations and environments in which residential electricity meters typically participate in information exchange, optical bi-directional communications interfaces are often preferred for use in residential electricity meters. Optical communications interfaces are preferred because they are cost effective while providing sufficient reliability and relative ease of use when compared to other communications interfaces that require physical connections.
In general terms, infrared bi-directional optical interfaces for electricity meters require a transmitter, a receiver, and supporting electronics to convert infrared light into appropriate electrical signals and vice-versa. Because the infrared transmitter is usually implemented employing only two discrete electronic components in the form of a light emitting diode and a current limiting resistor, opportunities for cost savings are limited. However, numerous circuits are used for infrared receivers in electricity meters. By implementing an optical receiver having relatively few electronic components, the meter manufacturer will achieve a cost savings that translates into a competitive advantage for the meter manufacturer.
Accordingly, it would be advantageous to provide a low cost receiver for a residential electricity meter that uses few electronic components.